| orbital fractures | Fractures of the bones in the orbit, which include parts of the frontal, ethmoidal, lacrimal, and sphenoid bones and the maxilla and zygoma. (12 Dec 1998) |
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| orbital gyri | A number of small, irregular convolutions occupying the concave inferior surface of each frontal lobe of the cerebrum. Synonym: gyri orbitales. (05 Mar 2000) |
| orbital hernia | Displacement of orbital fat through a defect in the orbital septum or Tenon's capsule into the subcutaneous tissues of the eyelid or subconjunctivally. (05 Mar 2000) |
| orbital implant | The glass, plastic, or metal device placed in the muscle cone after enucleation of an eye. (05 Mar 2000) |
| orbital index | Relation of the height of the orbit to its width: (orbital height × 100)/orbital width. (05 Mar 2000) |
| orbital lamina of ethmoid bone | A thin plate of ethmoid bone forming part of the medial wall of the orbit and the lateral wall for the ethmoidal labyrinth. Synonym: lamina orbitalis ossis ethmoidalis, lamina papyracea, orbital lamina of ethmoid bone, orbital layer of ethmoid bone, orbital plate, paper plate, papyraceous plate. (05 Mar 2000) |
| orbital layer of ethmoid bone | A thin plate of ethmoid bone forming part of the medial wall of the orbit and the lateral wall for the ethmoidal labyrinth. Synonym: lamina orbitalis ossis ethmoidalis, lamina papyracea, orbital lamina of ethmoid bone, orbital layer of ethmoid bone, orbital plate, paper plate, papyraceous plate. (05 Mar 2000) |
| orbital muscle | <anatomy> A rudimentary nonstriated muscle, crossing the infraorbital groove and sphenomaxillary fissure, intimately united with the periosteum of the orbit. Synonym: musculus orbitalis, Muller's muscle, orbital muscle. (05 Mar 2000) |
| orbital neoplasms | Neoplasms of the bony orbit and contents except the eyeball. (12 Dec 1998) |
| orbital nerve | <anatomy, nerve> A branch of the maxillary nerve in the inferior orbital fissure through which it passes; it gives rise to two sensory branches, the zygomaticotemporal and zygomaticofacial, which supply the skin of the temporal and zygomatic regions and is continued as the communicating branch of the lacrimal nerve with the zygomatic nerve. Synonym: nervus zygomaticus, orbital nerve, temporomandibular nerve. (05 Mar 2000) |
| orbital opening | The somewhat quadrangular anterior entrance to the orbit which forms the base of the pyramid-shaped orbital cavity. It is bounded by the sharp supra-, infra-, and lateral orbital margins and a less obvious medial margin on each side of the upper nose. Synonym: aditus orbitae, aperture of orbit. (05 Mar 2000) |
| orbital ophthalmoplegia | Ophthalmoplegia due to a lesion within the orbit. (05 Mar 2000) |
| orbital part of frontal bone | The portion of the frontal bone that contributes to the formation of the orbits; the most rostral of three cortical convolutions that togetther form the inferior frontal gyrus. Synonym: pars orbitalis ossis frontalis. (05 Mar 2000) |
| orbital part of lacrimal gland | See: lacrimal gland. (05 Mar 2000) |
| orbital part of optic nerve | <anatomy, nerve> The part of the optic nerve between the eye and the optic canal. Synonym: pars orbitalis nervi optici. (05 Mar 2000) |